Drug combination extends survival in metastatic breast cancer

Coadministration of anastrozole (Arimidex) and fulvestrant (Faslodex) prolonged survival more effectively than did anastrozole alone or sequential therapy with the two agents among women with hormone-receptor (HR)-positive metastatic breast cancer.

In the study leading to this finding, 707 postmenopausal women with previously untreated metastatic breast cancer were randomized to one of two groups. Members of group 1 received oral anastrozole 1 mg/day, with crossover to fulvestrant injection alone (500 mg on day 1 and 250 mg on days 14 and 28 and monthly thereafter) strongly encouraged if the disease progressed. The group 2 participants were given anastrozole and fulvestrant in combination. Anastrozole is an aromatase inhibitor; fulvestrant binds to estrogen receptors.

Median progression-free survival was 13.5 months in group 1, compared with 15 months in group 2. The combination-therapy patients also had longer overall survival (median 47.7 months, compared with 41.3 months), despite the fact that 41% of the women in group 1 crossed over to fulvestrant after disease progression. The rates of grades 3-5 toxic effects did not differ significantly between the two sets of patients, but three deaths that were possibly associated with treatment occurred in the combination-therapy group (N Engl J Med. 2012;367:435-444).

The coadministration of anastrozole and fulvestrant was superior to anastrozole therapy alone or anastrozole followed by fulvestrant, even with the fulvestrant dose being lower than the current standard.